The present invention relates to methods and apparatus for for high speed container placement, particularly for the purpose of filling and/or weighing a plurality of containers in a continuous operation.
In previous systems, particularly those patented by the present inventor and described in the following U.S. Pat. Nos. 4,848,479; 4,753,275; 4,657,054 and 4,625,775 (the disclosures of which are incorporated by reference herein), systems were devised to handle container placement for either top-off filling, complete filling or check weighing. Such systems served to transfer, on the one hand, a plurality of containers between a supply or feed conveyer, via transfer devices on a turntable, to stationary receiving stations (i.e. weighing stations or load cells) and thence back again from the load cells to the supply conveyer, or, on the other hand, between a straight line conveyer directly to either one or two stationary receiving stations and from there to a separate or second discharge conveyer. In both the machines, as just described, sufficient size must be allowed for to allow the multiple containers to be transferred by movable transfer guides rotated by the turntable to the receiving stations and from the receiving stations back to the supply conveyer, in the case of the rotary machine, or to a separate discharge conveyer, in the case of the straight-line machine. In the case of the rotary machines, considerable space is taken up by the rotating turntable and the driving mechanisms for the transfer guides associated with the transfer devices on the turntable which transport the containers on their cycloidally curved paths to and from the load cells. In the case of the straight line machine, again considerable size and bulk are required to accommodate a discharge conveyer system separate from the feeder or supply conveyer as well as the stationary transfer guides that have to operate between the two conveyers. Also, the rest period allowed for processing the containers that is otherwise obtained in the rotary design is eliminated in the straight line machines, so that the weighing time will be very short (less than half of the cycling time of the 360 degree rotations of these transfer devices around their respective drive shafts). Since the speed of these constantly rotating transfer devices must be close to the speed of the conveyer at the moment of pick-up of a container, the cycling time for a 360 degree revolution is so short that the conveyer can only supply two containers at the most during the cycling time, which then necessarily limits these straight line machines to only two load cells, that is, two receiving or processing stations. Consequently, the containers in such machines can no longer be returned to the supply conveyer (as in the rotary machines) but must be placed on a separate conveyer running parallel to the supply conveyer on the opposite side of the transfer device from the supply conveyer. As a result of the aforementioned conditions in previously known straight line machines, their weighing or processing time is extremely short and their capacity limited, requiring, therefore, the addition of a second conveyer and additional related equipment for operating such a conveyer.
In each of the aforementioned cases interference between the moving transfer guide members and the containers they handle poses a serious problem. Such interference can occur at almost any time between the transfer members when they do not properly handle the containers, such as tipping over the container before it is grasped, or knocking over one container in attempting to grasp another. Attempts to eliminate such interference have been made in the past by using large planetary gear transmissions or geneva drives which serve to accelerate and decelerate the motion of the guide members along their curved paths to and from the receiving stations. But such known transmission gearing systems cannot accelerate or decelerate enough the guides just before or after they reach their momentary maximum speed and for that reason are insufficient in preventing the aforementioned interference. Other means must be used to reduce interference, such as running the supply conveyer at a speed which is greater than the momentary maximum speed of the transfer guides and, also, implementing greater articulation into the construction of the transfer guide grasping mechanisms.
There is a need, therefore, for a high speed weighing system that can overcome the limitations of restricted rest periods for the placement and processing of containers, as well as a need to overcome the requirement for an additional conveyer in known straight line machines. Also there is a need to overcome the aforementioned interference problem between the transfer guide members and the containers they are meant to handle during a continuous placement operation, without having recourse to complicated speed transmission devices, such as planetary gearing systems, and complicated and expensive transfer guide members. Also, there is a need generally for a high-speed straight line line weighing system which will operate with fewer parts than previous systems and which will afford a cost-saving, space-saving and time-saving operation than was previously available.